Compositions for affecting weight loss

ABSTRACT

Disclosed are compositions for affecting weight loss comprising a first compound and a second compound, where the first compound is an opioid antagonist and the second compound causes increased agonism of a melanocortin 3 receptor (MC3-R) or a melanocortin 4 receptor (MC4-R) compared to normal physiological conditions. Also disclosed are methods of affecting weight loss, increasing energy expenditure, increasing satiety in an individual, or suppressing the appetite of an individual, comprising identifying an individual in need thereof and treating that individual to antagonize opioid receptor activity and to enhance α-MSH activity.

RELATED APPLICATIONS

[0001] The present application claims priority to the ProvisionalApplication Ser. No. 60/466,838, filed on Apr. 29, 2003, by Weber etal., and entitled “COMPOSITIONS FOR AFFECTING WEIGHT LOSS,” the entiredisclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention is in the field of pharmaceuticalcompositions and methods for the treatment of obesity and for affectingweight loss in individuals.

[0004] 2. Description of the Related Art

[0005] Obesity is a disorder characterized by the accumulation of excessfat in the body. Obesity has been recognized as one of the leadingcauses of disease and is emerging as a global problem. Increasedinstances of complications such as hypertension, non-insulin dependentdiabetes mellitus, arteriosclerosis, dyslipidemia, certain forms ofcancer, sleep apnea, and osteoarthritis have been related to increasedinstances of obesity in the general population.

[0006] Obesity has been defined in terms of body mass index (BMI). BMIis calculated as weight (kg)/[height (m)]². According to the guidelinesof the U.S. Centers for Disease Control and Prevention (CDC), and theWorld Health Organization (WHO) (World Health Organization. Physicalstatus: The use and interpretation of anthropometry. Geneva,Switzerland: World Health Organization 1995. WHO Technical ReportSeries), for adults over 20 years old, BMI falls into one of thesecategories: below 18.5 is considered underweight, 18.5-24.9 isconsidered normal, 25.0-29.9 is considered overweight, and 30.0 andabove is considered obese.

[0007] Prior to 1994, obesity was generally considered a psychologicalproblem. The discovery of the adipostatic hormone leptin in 1994 (Zhanget al., “Positional cloning of the mouse obese gene and its humanhomologue,” Nature 1994; 372:425-432) brought forth the realizationthat, in certain cases, obesity may have a biochemical basis. Acorollary to this realization was the idea that the treatment of obesitymay be achieved by chemical approaches. Since then, a number of suchchemical treatments have entered the market. The most famous of theseattempts was the introduction of Fen-Phen, a combination of fenfluramineand phentermine. Unfortunately, it was discovered that fenfluraminecaused heart-valve complications, which in some cases resulted in thedeath of the user. Fenfluramine has since been withdrawn from themarket. There has been some limited success with other combinationtherapy approaches, particularly in the field of psychological eatingdisorders. One such example is Devlin, et al., Int. J. Eating Disord.28:325-332, 2000, in which a combination of phentermine and fluoxetineshowed some efficacy in the treatment of binge eating disorders. Ofcourse, this disorder is an issue for only a small portion of thepopulation.

[0008] In addition to those individuals who satisfy a strict definitionof medical obesity, a significant portion of the adult population isoverweight. These overweight individuals would also benefit from theavailability of an effective weight-loss composition. Therefore, thereis an unmet need in the art to provide pharmaceutical compositions thatcan affect weight loss without having other adverse side effects.

SUMMARY OF THE INVENTION

[0009] Disclosed are compositions for affecting weight loss comprising afirst compound and a second compound, where the first compound is anopioid antagonist and the second compound causes increased agonism of amelanocortin 3 receptor (MC3-R) or a melanocortin 4 receptor (MC4-R)compared to normal physiological conditions.

[0010] Also disclosed are methods of affecting weight loss, increasingenergy expenditure, increasing satiety in an individual, or suppressingthe appetite of an individual, comprising identifying an individual inneed thereof and treating that individual to antagonize opioid receptoractivity and to enhance α-MSH activity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Arcuate nucleus neurons are known to be responsive to a widearray of hormones and nutrients, including leptin, insulin, gonadalsteroids, and glucose. In addition to potential transport mechanisms,peripheral substances may access these neurons via arcuate cell bodiesin and projections to the median eminence, a region considered to be acircumventricular organ, which lacks a blood-brain barrier. Cone et al.,“The arcuate nucleus as a conduit for diverse signals relevant to energyhomeostasis,” Int'l Journal of Obesity (2001) 25, Suppl 5, S63-S67.

[0012] Administration of exogenous leptin activates a number ofdifferent neurons in hypothalamic and brainstem cell groups that bearleptin receptor. Leptin-responsive neurons in the arcuate nucleusinclude both those containing neuropeptide Y (NPY) and agouti-relatedpeptide (AgRP) in the medial part of the nucleus and those containingboth pro-opiomelanocortin (POMC) and its derivatives, includingα-melanocyte stimulating hormone (α-MSH), as well as cocaine andamphetamine-related transcript (CART). Saper et al., “The need to feed:Homeostatic and hedonic control of eating,” Neuron, 36:199-211 (2002).

[0013] The leptin-responsive POMC neurons in the arcuate nucleus arethought to cause anorexia and weigh reduction by means of the action ofα-MSH on melanocortin 3 and/or 4 receptors (MC3-R, MC4-R). The highestMC3-R expression level is in the hypothalamus and limbic system, whereasMC4-R mRNA is expressed in virtually all major brain regions. Some ofthe metabolic effects resulting from stimulation of MC4-R are decreasedfood intake and an increase in energy expenditure through stimulation ofthyrotropin-releasing hormone and activation of the sympathetic nervoussystem. Targeted deletion of the MC4-R gene produces obesity,hyperphagia, hyperinsulinemia, and reduced energy expenditure. Targeteddeletion of MC3-R results in increased adiposity due to decreased energyexpenditure. Korner et al., “The emerging science of body weightregulation and its impact on obesity treatment,” J. Clin. Invest.111(5):565-570 (2003). Thus, increased concentrations of α-MSH in thecentral nervous system (CNS) increase its action on MC3-R and/or MC4-Rand result in a suppressed appetite.

[0014] POMC neurons also release β-endorphin when they release α-MSH.β-endorphin is an endogenous agonist of the 1-opioid receptors (MOP-R),found on the POMC neurons. Stimulation of MOP-R decreases the release ofα-MSH. This is a biofeedback mechanism that under normal physiologicalconditions controls the concentration of α-MSH in the CNS. Thus,blocking MOP-R by opioid antagonists will break the feedback mechanism,which results in continued secretion of α-MSH and an increase in itsconcentration in the CNS.

[0015] A second population of neurons in the arcuate nucleus tonicallyinhibits the POMC neurons. These POMC-inhibiting neurons secrete NPY,the neurotransmitter γ-aminobutyric acid (GABA), and AgRP. NPY and GABAinhibit POMC neurons, via NPY Y1 receptors and GABA receptors,respectivley. Thus, within the arcuate nucleus NPY and GABA inhibit therelease of α-MSH, and therefore are stimulators of feeding. It is knownthat leptin inhibits the release of GABA from NPY terminals synapsingonto POMC neurons, whereas ghrelin, an orexigenic peptide, stimulatesthe ghrelin receptors on NPY neurons and increase the secretion of NPYand GABA onto the POMC cells, which in turn inhibits the release ofα-MSH.

[0016] AgRP stimulates food intake in the rat through antagonism of theinteraction of α-MSH at MC4-R. Expression of the AgRP gene is suppressedby leptin.

[0017] Serotonin, also known as 5-hydroxytryptamine or 5-HT, activatesthe POMC neurons to secrete α-MSH. However, serotonin is taken up andremoved from action by specific transporters so that a single serotoninmolecule has short term effects. It is known that selective serotoninre-uptake inhibitors (SSRIs) prevent the uptake of serotonin andincrease its concentrations in the CNS. Thus, SSRIs also increase thesecretion of α-MSH and its concentrations in the CNS.

[0018] Therefore, increased secretion of α-MSH through variousmechanisms, such as serotonin re-uptake inhibition, are among thestrategies that the methods and pharmaceutical compositions of thepresent invention pursue in order to produce a biochemical anorexigeniceffect.

[0019] The present invention provides a multi-faceted combinationtherapy approach to the problem of weight loss. It addresses not justsingle molecules, messengers, or receptors, but instead acts on multiplepoints in the feeding and satiety pathway. Aspects of the presentinvention are directed to increasing the concentrations of α-MSH in theCNS by stimulating the release of A-MSH, suppressing its metabolism,reducing the antagonism of its interaction at MC3/4-R, and suppressingany feedback mechanisms that slow or stop its release. Aspects of thepresent invention include pharmaceutical compositions whose componentsachieve one or more of these functions. The present inventors havediscovered that a combination of two or more of the compounds disclosedherein results in a synergistic effect that affects weight loss morequickly and on a more permanent basis.

[0020] Thus, in a first aspect, the present invention is directed to acomposition for the treatment of obesity or for affecting weight losscomprising a first compound and a second compound, where the firstcompound is an opioid antagonist and the second compound causesincreased agonism of a melanocortin 3 receptor (MC3-R) or a melanocortin4 receptor (MC4-R) compared to normal physiological conditions.

[0021] In certain embodiments, the second compound causes increasedactivity of the POMC neurons, leading to greater agonism at MC3-R and/orMC4-R.

[0022] In certain embodiments the opioid antagonist antagonizes aμ-opioid receptor (MOP-R) in a mammal. The mammal may be selected fromthe group consisting of mice, rats, rabbits, guinea pigs, dogs, cats,sheep, goats, cows, primates, such as monkeys, chimpanzees, and apes,and humans.

[0023] In some embodiments the opioid antagonist is selected from thegroup consisting of alvimopan, norbinaltorphimine, nalmefene, naloxone,naltrexone, methylnaltrexone, and nalorphine, and pharmaceuticallyacceptable salts or prodrugs thereof.

[0024] In other embodiments, the opioid antagonist is a partial opioidagonist. Compounds of this class have some agonist activity at opioidreceptors. However, because they are weak agonists, they function asde-facto antagonists. Examples of partial opioid agonists includepentacozine, buprenorphine, nalorphine, propiram, and lofexidine.

[0025] The term “pharmaceutically acceptable salt” refers to aformulation of a compound that does not cause significant irritation toan organism to which it is administered and does not abrogate thebiological activity and properties of the compound. Pharmaceutical saltscan be obtained by reacting a compound of the invention with inorganicacids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitricacid, phosphoric acid, methanesulfonic acid, ethanesulfonic acid,p-toluenesulfonic acid, salicylic acid and the like. Pharmaceuticalsalts can also be obtained by reacting a compound of the invention witha base to form a salt such as an ammonium salt, an alkali metal salt,such as a sodium or a potassium salt, an alkaline earth metal salt, suchas a calcium or a magnesium salt, a salt of organic bases such asdicyclohexylamine, N-methyl-D-glucamine, tris(hydroxymethyl)methylamine, and salts thereof with amino acids such as arginine,lysine, and the like.

[0026] A “prodrug” refers to an agent that is converted into the parentdrug in vivo. Prodrugs are often useful because, in some situations,they may be easier to administer than the parent drug. They may, forinstance, be bioavailable by oral administration whereas the parent isnot. The prodrug may also have improved solubility in pharmaceuticalcompositions over the parent drug, or may demonstrate increasedpalatability or be easier to formulate. An example, without limitation,of a prodrug would be a compound of the present invention which isadministered as an ester (the “prodrug”) to facilitate transmittalacross a cell membrane where water solubility is detrimental to mobilitybut which then is metabolically hydrolyzed to the carboxylic acid, theactive entity, once inside the cell where water-solubility isbeneficial. A further example of a prodrug might be a short peptide(polyaminoacid) bonded to an acid group where the peptide is metabolizedto provide the active moiety.

[0027] In certain embodiments, the second compound in the pharmaceuticalcompositions of the present invention triggers the release ofα-melanocyte stimulating hormone (α-MSH). The second compound mayincrease the extracellular serotonin concentrations in the hypothalamus.In some embodiments, the second compound is selected from the groupconsisting of a selective serotonin reuptake inhibitor (SSRI), aserotonin 2C agonist, and a serotonin 1B agonist. In furtherembodiments, the second compound is selected, e.g., from the groupconsisting of fluoxetine, fluvoxamine, sertraline, paroxetine,citalopram, escitalopram, sibutramine, duloxetine, atomoxatine, andvenlafaxine, and pharmaceutically acceptable salts or prodrugs thereof.

[0028] The terms “serotonin 1B receptor,” “serotonin 2C receptor,”“5-HT1b receptor,” and “5-HT2c receptor” refer to receptors found morecommonly in rodents. It is understood by those of skill in the art thatother mammals have serotonin receptors on various neurons that areanalogous in function and form to these receptors. Agonists orantagonists at these non-rodent, preferably human, serotonin receptorsare within the scope of the present invention.

[0029] In certain embodiments, the second compound suppresses theexpression of the AgRP gene or the production or release ofagouti-related protein (AgRP). In some of these embodiments, the secondcompound suppresses the activity of neurons that express AgRP.

[0030] In other embodiments, the second compound suppresses theexpression of the NPY gene or the production or release of neuropeptideY (NPY). In some of these embodiments, the second compound suppressesthe activity of neurons that express NPY. In further embodiments, thesecond compound is selected from the group consisting of NPYantagonists, ghrelin antagonists, and leptin. In certain otherembodiments, the second compound agonizes NPY Y2 receptor.

[0031] Other embodiments of the present invention include those in whichthe second compound is selected from the group consisting of a γ-aminobutyric acid (GABA) inhibitor, a GABA receptor antagonist, and a GABAchannel antagonist. By “GABA inhibitor” it is meant a compound thatreduces the production of GABA in the cells, reduces the release of GABAfrom the cells, or reduces the activity of GABA on its receptors, eitherby preventing the binding of GABA to GABA receptors or by minimizing theeffect of such binding. The GABA inhibitor may be a 5-HT1b agonist oranother agent that inhibits the activity of NPY/AgRP/GABA neurons. Inaddition, the GABA inhibitor may suppress the expression of the AgRPgene, or the GABA inhibitor may suppress the production or release ofAgRP. It is, however, understood that a 5-HT1b agonist may inhibit theNPY/AgRP/GABA neuron (and therefore activate POMC neurons) withoutacting as an inhibitor of the GABA pathway.

[0032] In certain other embodiments the GABA inhibitor increases theexpression of the POMC gene. In some of these embodiments, the GABAinhibitor increases the production or release of pro-opiomelanocortin(POMC) protein. In certain other of these embodiments, the GABAinhibitor increases the activity on POMC expressing neurons. In someembodiments, the GABA inhibitor is topiramate.

[0033] In other embodiments the second compound is a dopamine reuptakeinhibitor. Phentermine is an example of a dopamine reuptake inhibitor.In certain other embodiments, the second compound is a norepinephrinereuptake inhibitor. Examples of norepinephrine reuptake inhibitorsinclude bupropion, thionisoxetine, and reboxetine. Other embodimentsinclude those in which the second compound is a dopamine agonist. Somedopamine agonists that are available on the market include cabergoline,amantadine, lisuride, pergolide, ropinirole, pramipexole, andbromocriptine. In further embodiments, the second compound is anorepinephrine releaser, for example diethylpropion, or a mixeddopamine/norepinephrine reuptake inhibitor, for example, atomoxatine.

[0034] In certain other embodiments, the second compound is a 5-HT1bagonist, such as sumatriptan, almotriptan, naratriptan, frovatriptan,rizatriptan, zomitriptan, and elitriptan.

[0035] In further embodiments, the second compound is an anticonvulsant.The anticonvulsant may be selected from the group consisting ofzonisamide, topiramate, nembutal, lorazepam, clonazepam, clorazepate,tiagabine, gabapentin, fosphenyloin, phenyloin, carbamazepine,valproate, felbamate, levetiracetam, oxcarbazepine, lamotrigine,methsuximide, and ethosuxmide.

[0036] In some embodiments, the second compound is a cannabinoidreceptor antagonist. Examples of this group of compounds include AM251[N-(piperidin-1-yl)-1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-1H-pyrazole-3-carboxamide],AM281[N-(morpholin-1-yl)-1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-1H-pyrazole-3-carboxamide],AM630(6-iodo-2-methyl-1-[2-(4-morpholinyl)ethyl]-1H-indol-3-yl](4-methoxyphenyl)methanone),LY320135, and SR141716A (rimonabant), and pharmaceutically acceptablesalts or prodrugs thereof. LY320135 and SR141716A have the followingstructures.

[0037] In certain embodiments, the second compound itself may be acombination of two or more compounds. For example, the second compoundmay be a combination of a dopamine reuptake inhibitor and anorepinephrine reuptake inhibitor, e.g. bupropion and mazindol.Alternatively, the second compound may be a combination of a SSRI and anorepinephrine reuptake inhibitor, such as sibutramine, venlafaxine, andduloxetine.

[0038] In certain embodiments, the second compound is an activator ofthe POMC neurons. Examples of POMC activators include Ptx1 andinterleukin 1 beta, (IL-1β).

[0039] In another aspect, the present invention relates to a method ofaffecting weight loss, comprising identifying an individual in needthereof and treating that individual to antagonize opioid receptoractivity and to enhance α-MSH activity.

[0040] In certain embodiments, the individual has a body mass index(BMI) greater than 25. In other embodiments, the individual has a BMIgreater than 30. In still other embodiments, the individual has a BMIgreater than 40. However, in some embodiments, the individual may have aBMI less than 25. In these embodiments, it may be beneficial for healthor cosmetic purposes to affect weight loss, thereby reducing the BMIeven further.

[0041] In some embodiments, opioid receptor activity is antagonized byadministering an opioid receptor antagonist. The opioid receptorantagonist may be a MOP receptor antagonist. In some embodiments, theopioid receptor antagonist is selected from alvimopan,norbinaltorphimine, nalmefene, naloxone, naltrexone, methylnaltrexone,and nalorphine, and pharmaceutically acceptable salts or prodrugsthereof.

[0042] In some of the embodiments set forth above, α-MSH activity isenhanced by administering a compound, where the compound triggersrelease of α-MSH or increases the activity of neurons that expressα-MSH. In some embodiments, the compound is a selective serotoninreuptake inhibitor (SSRI) or a specific 5-HT receptor agonist. Examplesof SSRIs that can be used in the present invention include fluoxetine,fluvoxamine, sertraline, paroxetine, citalopram, escitalopram,sibutramine, duloxetine, and venlafaxine, and pharmaceuticallyacceptable salts or prodrugs thereof.

[0043] In other embodiments, the compound is a γ-amino butyric acid(GABA) inhibitor. The GABA inhibitor may be a 5-HT1b receptor agonist.The GABA inhibitor may suppress the expression of the AgRP gene, or itmay suppresses the production or release of AgRP. The GABA inhibitor maysuppress the expression or release of NPY. In certain embodiments, theGABA inhibitor suppresses the activity of neurons that express AgRP. Forexample, the GABA inhibitor may be topiramate,1-(2-(((diphenylmethylene)amino)oxy)ethyl)-1,2,5,6-tetrahydro-3-pyridinecarboxylicacid hydrochloride (NNC-711), or vigabatrin.

[0044] In certain embodiments, the method of invention set forth aboveis practiced with the proviso that the individual is not suffering fromPrader-Willi syndrome or binge eating disorder. Thus, some embodimentsof the invention are to be distinguished from combination therapyinvolving SSRI anti-depressants (e.g., fluoxetine) used to treatphysiological eating disorders such as binge eating disorder orPrader-Willi syndrome. In these embodiments, the target population isthe population of individuals needing or desiring weight loss, apartfrom needing treatment for Prader-Willi syndrome or binge eatingdisorder.

[0045] Individuals suffering from depression may gain weight as a resultof their depression. In addition, certain depressed individuals gainweight as a side effect of the depression therapy. In certainembodiments, the method of invention set forth above is practiced withthe proviso that the individual is not suffering from depression. Insome embodiments, the individual's overweight state was not caused bytreatment for depression.

[0046] In other embodiments, the method of the invention set forth aboveis practiced with the proviso that if the opioid receptor is antagonizedusing naltrexone, then release of α-MSH is not stimulated withfluoxetine. However, the combination of naltrexone with fluoxetine maybe used to affect weight loss in individuals who wish to lose weight,whether or not they are clinically categorized as obese. Theseindividuals may include those with BMI of greater than 25, or thoseindividuals with BMI of less than 25 who still wish to lose additionalweight. This particular combination may also be used for the treatmentof general obesity. In certain embodiments, the individual who wishes tolose additional weight does not suffer from binge eating disorder.

[0047] In some embodiments, the treating step of the above methodcomprises administering to the individual a first compound and a secondcompound, where the first compound is an opioid antagonist and thesecond compound enhances α-MSH activity.

[0048] In some embodiments the first compound and the second compoundare administered more or less simultaneously. In other embodiments thefirst compound is administered prior to the second compound. In yetother embodiments, the first compound is administered subsequent to thesecond compound.

[0049] In certain embodiments, the first compound and the secondcompound are administered individually. In other embodiments, the firstcompound and the second compound are covalently linked to each othersuch that they form a single chemical entity. The single chemical entityis then digested and is metabolized into two separate physiologicallyactive chemical entities, one of which is the first compound and theother one is the second compound.

[0050] In some embodiments, the compositions of the present inventionare a combination of the following compounds:

[0051] a SSRI in combination with a dopamine reuptake inhibitor, adopamine/norepinephrine reuptake inhibitor, a norepinephrine reuptakeinhibitor, an opioid antagonist, a partial opioid agonist, GABAinhibitor, a peripherally acting weight loss agent such as metformin, ora peptide, such as PYY, PYY₃₋₃₆, or leptin;

[0052] Serotonin in combination with a dopamine reuptake inhibitor, adopamine/norepinephrine reuptake inhibitor, an opioid antagonist, apartial opioid agonist, or a GABA inhibitor;

[0053] a dopamine reuptake inhibitor in combination with anorepinephrine reuptake inhibitor, a norepinephrine releaser, anorepinephrine agonist, an opioid antagonist, a partial opioid agonist,a GABA inhibitor, an adenosine compound, a cholinergic receptorantagonist, or a peptide, such as PYY, PYY₃₋₃₆, or leptin;

[0054] a dopamine/norepinephrine reuptake inhibitor in combination withan opioid antagonist, a partial opioid agonist, a GABA inhibitor, or aperipherally acting weight loss agent such as metformin;

[0055] a dopamine agonist in combination with an opioid antagonist, apartial opioid agonist, a GABA inhibitor, or a peptide, such as PYY,PYY₃₋₃₆, or leptin.

[0056] Examples of norepinephrine agonists include phendimetrazine andbenzphetamine. Examples of adenosine compounds include all xanthinederivatives, such as adenosine, caffeine, theophylline, theobromine, andaminophylline. An example of acholinergic receptor antagonist isnicotine.

[0057] In another aspect, the present invention relates to a method ofincreasing satiety in an individual comprising identifying an individualin need thereof and treating that individual to antagonize opioidreceptor activity and to enhance α-MSH activity.

[0058] In some embodiments, the treating step of the above methodcomprises administering to the individual a first compound and a secondcompound, where the first compound is an opioid antagonist and thesecond compound enhances α-MSH activity.

[0059] In some embodiments the first compound and the second compoundare administered nearly simultaneously. In other embodiments the firstcompound is administered prior to the second compound. In yet otherembodiments, the first compound is administered subsequent to the secondcompound.

[0060] In yet another aspect, the present invention relates to a methodof suppressing the appetite of an individual comprising identifying anindividual in need thereof and treating that individual to antagonizeopioid receptor activity and to enhance α-MSH activity.

[0061] In some embodiments, the treating step of the above methodcomprises administering to the individual a first compound and a secondcompound, where the first compound is an opioid antagonist and thesecond compound enhances α-MSH activity.

[0062] In some embodiments the first compound and the second compoundare administered nearly simultaneously. In other embodiments the firstcompound is administered prior to the second compound. In yet otherembodiments, the first compound is administered subsequent to the secondcompound.

[0063] In another aspect, the present invention relates to a method ofincreasing energy expenditure in an individual comprising identifying anindividual in need thereof and treating that individual to antagonizeopioid receptor activity and to enhance α-MSH activity.

[0064] In some embodiments, the treating step of the above methodcomprises administering to the individual a first compound and a secondcompound, where the first compound is an opioid antagonist and thesecond compound enhances α-MSH activity.

[0065] In some embodiments the first compound and the second compoundare administered nearly simultaneously. In other embodiments the firstcompound is administered prior to the second compound. In yet otherembodiments, the first compound is administered subsequent to the secondcompound.

[0066] In certain embodiments disclosed herein, an individual is given apharmaceutical composition comprising a combination of two or morecompounds to affect weight loss. In some of these embodiments, eachcompound is a separate chemical entity. However, in other embodiments,the two compounds are joined together by a chemical linkage, such as acovalent bond, so that the two different compounds form separate partsof the same molecule. The chemical linkage is selected such that afterentry into the body, the linkage is broken, such as by enzymatic action,acid hydrolysis, base hydrolysis, or the like, and the two separatecompounds are then formed.

[0067] Thus, in another aspect, the present invention relates tosynthetic routes to novel molecules in which an opioid antagonist islinked by a flexible linker to a selective serotonin reuptake inhibitor(SSRI).

[0068] Data from previous structure-activity relationship (SAR) studieswithin the family of μ opioid antagonists may be used as a guide todetermine which antagonists to use and the optimal position or positionson the antagonist molecules to attach the tether such that potency andselectivity of the antagonist will remain high. Similarly, SAR datawithin the family of SSRIs may be used as a guide to determine whichinhibitors to use and the optimal position or positions on theinhibitors to attach the tether such that potency and selectivity remainhigh. The tether or linker moiety is chosen from among those ofdemonstrated utility for linking bioactive molecules together. Disclosedherein are representative opioid antagonists, linkers and SSRI moleculesthat can be attached together in different combinations to formheterobivalent therapeutic molecules.

[0069] Structure-activity relationships of the opioid agonists andantagonists have been reviewed. See for example, Zimmerman, D. M.;Leander, J. D. J. Med. Chem. 1990, 33, 895; Portoghese, P. S. J. Med.Chem. 1992, 35, 1927; Carroll, F. I. J. Med. Chem. 2003, 46, 1. Theopioid antagonists, nalmefene (1), naltrexone (2), naloxone (3) andnaltrexamine (4) are thebaine-derived structures that share a commonopiate-type template. 1-Subtype selective opioid antagonists are ofconsiderable current interest as agents for the treatment of obesity(Glass, M. J.; Billington, C. J.; Levine, A. S. Neuropeptides 1999, 33,350) and CNS disorders (Reneric, J. P.; Bouvard, M. P. CNS Drugs 1998,10, 365).

[0070] N-Methyl and N-2-phenylethyl substituted opioids tend to showopioid agonist activity whereas N-allyl and N-cyclopropylmethylsubstituted analogs tend to show opioid antagonist activity. AnyN-attached linker moiety will be larger than methyl. Provided that thelinker moiety does not mimic 2-phenylethyl, such linked opioids areexpected to behave as opioid antagonists. Therefore, the nitrogen atomof nalmefene and naltrexone (and naloxone) is a suitable site forattachment of a linker moiety. Less SAR information is available withregard to substitution at other sites on these opioids, however,attachment of the linker unit to one or the other of the carbon atomsbearing one or more hydrogen atoms remains an option.

[0071] Both nalmefene and naltrexone are potent μ-opioid antagonists.The only structural difference is that nalmefene has a methylene groupin place of the ketone oxygen atom in naltrexone. It is thus postulatedthat significant changes in structure at the ketone oxygen site innaltrexone do not significantly affect antagonist potency. Therefore, alinker may be attached to the methylene group in nalmefene withoutsignificant reduction in antagonist potency. Carbonyl derivatives ofnaloxone are well known and include symmetrical azine (═N—N═), mixedazine (Schmidhammer, H.; Kaspar, F.; Marki, A.; Borsodi, A. Helv. Chim.Acta 1994, 77, 999), hydazone (Hahn, E. F.; Itzhak, Y.; Nishimura, S.;Johnson, N.; Pasternak, G. W. J. Pharm. Exper. Therapeutics 1985, 235,846-50), semicarbazone and thiosemicarbazone derivatives (Kolb, V. M.;Koman, A.; Neil, A. Pharmaceutical Res. 1985, 6, 266-71). Naloxazone,the hydrazone of naloxone, is an irreversible, selective and long actingantagonist of the μ-1 subclass of the opioid receptors (Pasternak, G.W.; Hahn, E. F. J. of Med. Chem. 1980, 23, 674-6). Certain of thederivatives are potent μ opioid antagonists while others are potentagonists.

[0072] Naltrexamine (4) has been linked by attachment of its primaryamino group to a wide variety of other molecules producing, for example,a fluorogenic opioid receptor affinity label (Le Bourdonnec, B.; ElKouhen, R.; Lunzer, M. M.; Law, P. Y.; Loh, H. H.; Portoghese, P. S.; J.Med. Chem.; 2000; 43; 2489-2492), an extensive series of nonequilibriumopioid agonists and antagonists (Sayre, L. M.; Larson, D. L.; Takemori,A. E.; Portoghese, P. S. J. Med. Chem. 1984, 27, 1325), and a series ofpotent bivalent opioid antagonists (Erez, M.; Takemori, A. E.;Portoghese, P. S. J. Med. Chem. 1982, 25, 847-849). Consequently, theprimary amino group of naltrexamine constitutes a suitable site forattachment of a linker moiety.

[0073] A limited SAR for fluoxetine (5) has been published in U.S. Pat.No. 4,214,081, incorporated by reference herein in its entirety.N-Methylfluoxetine (6) shows comparable potency and selectivity to thatof fluoxetine toward inhibition of serotonin reuptake. Therefore,attachment of a linker to the nitrogen atom of fluoxetine can result inretention of the potency and selectivity of fluoxetine itself. However,the present disclosure is not limited to the fluoxetine series of SSRIs.It is envisaged that a variety of SSRI molecules such as paroxetine(Dechant, K. L.; Clissold, S. P. Drugs, 1991, 41, 225-253) or one or theother of the bivalent SSRIs described by Kozikowski et al. (Tamiz, A.P.; Zhang, J.; Zhang, M.; Wang, C. Z.; Johnson, K. M.; Kozikowski, A. P.J. Am. Chem. Soc. 2000, 122, 5393-5394; Tamiz, A. P.; Bandyopadhyay, B.C.; Zhang, J.; Flippen-Anderson, J. L.; Zhang, M.; Wang, C. Z.; Johnson,K. M.; Tella, S.; Kozikowski, A. P. J. Med. Chem. 2001, 44, 1615-1622)may also be utilized to construct the heterobivalent therapeuticmolecules of this invention.

[0074] Examples of linkers reported in the scientific literature includemethylene (CH₂)_(n) linkers (Hussey, S. L.; Muddana, S. S.; Peterson, B.R.; J. Am. Chem. Soc. 2003; 125; 3692-3693; Tamiz, A. P.; Bandyopadhyay,B. C.; Zhang, J.; Flippen-Anderson, J. L.; Zhang, M.; Wang, C. Z;Johnson, K. M.; Tellar, S.; Kozikowski, A. P. J. Med. Chem. 2001, 44,1615-1622), oligo ethyleneoxy O(—CH₂CH₂O—)_(n) units used to linknaltrexamine to other opioids, glycine oligomers of the formula—NH—(COCH₂NH)_(n)COCH₂CH₂CO—(NHCH₂CO)_(n)NH— used to link opioidantagonists and agonists together ((a) Portoghese, P. S.; Ronsisvalle,G.; Larson, D. L.; Yim, C. B.; Sayre, L. M.; Takemori, A. E. Life Sci.1982, 31, 1283-1286. (b) Portoghese, P. S.; Larson, D. L.; Sayre, L. M.;Yim, C. B.; Ronsisvalle, G.; Tam, S. W.; Takemori, A. E. J. Med. Chem.1986, 29, 1855-1861), hydrophilic diamines used to link opioid peptidestogether (Stepinski, J.; Zajaczkowski, I.; Kazem-Bek, D.; Temeriusz, A.;Lipkowski, A. W.; Tam, S. W. Internat. J. of Peptide & Protein Res.1991, 38, 588-92), rigid double stranded DNA spacers (Paar, J. M.;Harris, N. T.; Holowka, D.; Baird, B. J. Immunol. 2002, 169, 856-864)and the biodegradable linker poly (L-lactic acid) (Klok, H.-A.; Hwang,J. J.; Iyer, S. N.; Stupp, S. I. Macromolecules 2002, 35, 746-759). Theattachment of the tether to the antagonist can result in the antagonistachieving a favorable binding orientation. The linker itself may or maynot be biodegradable. The linker may take the form of a prodrug and betunable for optimal release kinetics of the linked drugs. The linker maybe either conformationally flexible throughout its entire length or elsea segment of the tether may be designed to be conformationallyrestricted (Portoghese, P. S.; Ronsisvalle, G.; Larson, D. L.; Takemori,A. E. J. Med. Chem. 1986, 29, 1650-1653).

[0075] In Scheme 1 below, naltrexone (2) is used in the linkingreaction. As a consequence of the Wittig reaction, a double bondreplaces the carbonyl group in naltrexone. The net result is fluoxetinelinked with a flexible methylene linker to a nalmefene molecule by wayof the nalmefene double bond.

[0076] Reductive amination of fluoxetine with an ω-bromoaldehyde such as11-bromoundecanal 6 (n=9) gives bromoamine 7 (n=9), best stored as thehydrobromide salt to prevent an unwanted slow macrocyclization sidereaction by way of attack of the free amino group on the carbon bearingthe bromine atom. Reaction of 7 with triphenylphosphine gives theintermediate phosphonium salt, which upon rection with butyllithiumgenerates the corresponding ylid 8 (n=9). A Wittig reaction between 8and the ketone group of naltrexone (2) gives the linked molecule 9containing a fluoxetine unit coupled to what is now a nalmefene unit.The expected mixture of cis, trans isomers about the newly introduceddouble bond is separable by standard chromatographic techniques. Ifracemic fluoxetine is used, then a mixture of two optically activediastereomers of 9 will be produced owing to the fact that a singleenantiomer 2 of naltrexone was used. Chemists skilled in the art willrecognize that the (CH₂)₉ linker may be varied in length and/or containsubstituents by beginning with a different bromoaldehyde. Thus,pharmacological properties may be optimized. Molecule 9 is stable underphysiological conditions. Opioid antagonist activity will be due to thecovalently linked nalmefene unit and not due to free nalmefene releasedas a result of some cleavage reaction. Similarly, SSRI activity will bedue to the covalently linked fluoxetine unit and not due to freefluoxetine released as a result of some cleavage reaction.

[0077] An analogous reaction sequence may be used in which thebromoaldehyde is derived from an oligo ethylene glycol as shown inScheme 2 below. For example, tetraethylene glycol (10 n=2) is convertedinto bromide 11 (n=2), which is then oxidized under Swern conditions toaldehyde 12 (n=2). Substitution of aldehyde 12 for aldehyde 6 in Scheme1 will give a series of irreversibly linked molecules in which thelinker is more hydrophilic than that in molecules 9. Generation of theylid in the oligo ethylene glycol series and the subsequent Wittigreaction is performed at reduced temperature to avoid β-elimination ofthe alkoxy group. If racemic fluoxetine is used, then a mixture of twooptically active diastereomers of 13 will be produced owing to the factthat a single enantiomer 2 of naltrexone was used. Chemists skilled inthe art will recognize that the (OCH₂CH₂)_(n) linker may be varied inlength by beginning with a different bromoaldehyde 12. Thus,pharmacological properties may be optimized. Molecule 13 is stable underphysiological conditions.

[0078] In Scheme 3, another linking method beginning with tetraethyleneglycol is illustrated as an example of a variety of oligo ethyleneglycols that may be used. Adapting the chemistry of Sashiwa et al.(Sashiwa, H.; Shigemasa, Y.; Roy, R. Macromolecules 2000, 33, 6913),tetraethylene glycol may be converted into acetal 14 (n=2) andsubsequently into aldehyde 15. Reductive amination of fluoxetine withaldehyde 15 gives the fluoxetine derivative 16. Reduction of azide 16 toamine 17 and then reductive amination with naltrexone gives molecule 18in which a fluoxetine unit is linked irreversibly by a flexible oligoethyleneoxy unit to β-naltrexamine (after separation of the α and βisomers). If racemic fluoxetine is used, then a mixture of two opticallyactive diastereomers of 18 will be produced owing to the fact that asingle enantiomer 2 of naltrexone was used. Chemists skilled in the artwill recognize that the (OCH₂CH₂)_(n) linker may be varied in length bybeginning with a different oligo ethylene glycol 10. Thus,pharmacological properties may be optimized. Molecule 18 should bestable under physiological conditions.

[0079] Scheme 4 illustrates a synthetic route to fluoxetine linked tonalmefene by way of the N-cyclopropyl group of nalmefene. The readilyavailable t-butyldimethylsilyl protected noroxymorphone (19) issynthesized from morphine (Ninan, A.; Sainsbury, M. Tetrahedron 1992,48, 6709-16), and then subjected to a reductive amination reaction withthe commercially available cyclopropanecarboxaldehyde 20 (Aldrich,largely trans) giving ester 21. Wittig methyleneation gives ester 22,which is hydrolyzed to give acid 23. Activation of acid 23 with anappropriate carbodiimide and then N-acylation of fluoxetine derivative17 (Scheme 3) gives 25, deprotection of which with Bu₄NF gives the novelmolecule 26. Chemists skilled in the art will recognize that the(OCH₂CH₂)_(n) linker may be varied in length by beginning with adifferent aldehyde azide 15 in the synthesis of 17. Thus,pharmacological properties may be optimized. Molecule 26 should bestable under physiological conditions.

[0080] Alternatively, ester 22 may be reduced to aldehyde 24 using DIBALat −78° C. Reductive amination of aldehyde 24 with amine 17 givesmolecule 27 after removal of the TBDMS protecting group. Chemistsskilled in the art will recognize that the (OCH₂CH₂)_(n) linker may bevaried in length by beginning with a different aldehyde azide 15 in thesynthesis of 17. Thus, pharmacological properties may be optimized.Molecule 27 should be stable under physiological conditions.

[0081] If the Wittig methyleneation step is omitted in the abovesequence, then an analog of 26, namely ketone 28, is formed in which themethylene group of 26 is replaced by a carbonyl group. The result is analtrexone unit linked to a fluoxetine unit by way of a flexible,hydrophilic (CH₂CH₂O)_(n) linker in the form of compound 28. Chemistsskilled in the art will recognize that the (OCH₂CH₂)_(n) linker may bevaried in length by beginning with a different aldehyde azide 15 in thesynthesis of 17. Thus, pharmacological properties may be optimized.Molecule 28 is stable under physiological conditions.

[0082] Scheme 5 illustrates how fluoxetine may be linked toβ-naltrexamine using a combination of linkers, namely the flexibleglycine-based linkers 29 exploited by Portoghese et al. and the oligoethylene glycol linkers used in the schemes above. Thus carboxylactivation of 29 with a suitable carbodiimide followed bymonocondensation with β-naltrexamine gives amide 30. Reactivation of 30followed by condensation with amine 17 (Scheme 3) gives molecule 31.Portoghese reports that symmetrical amides derived from linker 29 andβ-naltrexamine are effective μ-opioid receptor antagonists. Chemistsskilled in the art will recognize that the—NH—(COCH₂NH)_(n−1)COCH₂CH₂CO—(NHCH₂CO)_(n)NH— linker may be varied inlength by beginning with a different glycine-based linking unit 29 inthe synthesis of 30. Thus, pharmacological properties may be optimized.Molecule 31 is stable under physiological conditions.

[0083] Reaction of bromide 7 (Scheme 1) with Mg in dry THF will giveGrignard reagent 32, reaction of which with the carbonyl group ofnaltrexone gives adduct 33 after separation of the two diastereomersproduced at the newly created chiral center. Adduct 33 contains afluoxetine segment linked to a N-cyclopropylmethyl-normorphine unit byway of a flexible methylene linker. Chemists skilled in the art willrecognize that the (CH₂)₉ linker may be varied in length by beginningwith a different bromoaldehyde for the synthesis of bromide 7. Thus,pharmacological properties may be optimized. Molecule 33 is stable underphysiological conditions.

[0084] Throughout the above schemes, one should be able to employN-desmethylfluoxetine (34), or any other derivative of fluoxetine, inplace of fluoxetine. The resulting linked fluoxetine unit is identicalto that of fluoxetine itself except that the methyl group of fluoxetineis replaced by a longer chain that is part of the linker. When necessarydue to the use of strongly basic reagents or when chemoselectivitytoward a primary amino group elsewhere in the molecule is required, onemay protect the intermediate fluoxetine secondary amino group by use ofthe N-[2-(trimethylsilyl)ethoxy]methyl (SEM) group (Zeng, Z.; Zimmerman,S. C. Tetrahedron Lett. 1988, 29, 5123) as illustrated in Scheme 7.

[0085] In another aspect, the invention relates to a pharmaceuticalcomposition comprising a combination of an opioid antagonist and acompound that causes increased agonism of a melanocortin 3 receptor(MC3-R) or a melanocortin 4 receptor (MC4-R) compared to normalphysiological conditions, as described above, or comprising a linkedmolecule, as described herein, and a physiologically acceptable carrier,diluent, or excipient, or a combination thereof.

[0086] The term “pharmaceutical composition” refers to a mixture of acompound of the invention with other chemical components, such asdiluents or carriers. The pharmaceutical composition facilitatesadministration of the compound to an organism. Multiple techniques ofadministering a compound exist in the art including, but not limited to,oral, injection, aerosol, parenteral, and topical administration.Pharmaceutical compositions can also be obtained by reacting compoundswith inorganic or organic acids such as hydrochloric acid, hydrobromicacid, sulfuric acid, nitric acid, phosphoric acid, methanesulfonic acid,ethanesulfonic acid, p-toluenesulfonic acid, salicylic acid and thelike.

[0087] The term “carrier” defines a chemical compound that facilitatesthe incorporation of a compound into cells or tissues. For exampledimethyl sulfoxide (DMSO) is a commonly utilized carrier as itfacilitates the uptake of many organic compounds into the cells ortissues of an organism.

[0088] The term “diluent” defines chemical compounds diluted in waterthat will dissolve the compound of interest as well as stabilize thebiologically active form of the compound. Salts dissolved in bufferedsolutions are utilized as diluents in the art. One commonly usedbuffered solution is phosphate buffered saline because it mimics thesalt conditions of human blood. Since buffer salts can control the pH ofa solution at low concentrations, a buffered diluent rarely modifies thebiological activity of a compound.

[0089] The term “physiologically acceptable” defines a carrier ordiluent that does not abrogate the biological activity and properties ofthe compound.

[0090] The pharmaceutical compositions described herein can beadministered to a human patient per se, or in pharmaceuticalcompositions where they are mixed with other active ingredients, as incombination therapy, or suitable carriers or excipient(s). Techniquesfor formulation and administration of the compounds of the instantapplication may be found in “Remington's Pharmaceutical Sciences,” MackPublishing Co., Easton, Pa., 18th edition, 1990.

[0091] Suitable routes of administration may, for example, include oral,rectal, transmucosal, or intestinal administration; parenteral delivery,including intramuscular, subcutaneous, intravenous, intramedullaryinjections, as well as intrathecal, direct intraventricular,intraperitoneal, intranasal, or intraocular injections.

[0092] Alternately, one may administer the compound in a local ratherthan systemic manner, for example, via injection of the compounddirectly in the renal or cardiac area, often in a depot or sustainedrelease formulation. Furthermore, one may administer the drug in atargeted drug delivery system, for example, in a liposome coated with atissue-specific antibody. The liposomes will be targeted to and taken upselectively by the organ.

[0093] The pharmaceutical compositions of the present invention may bemanufactured in a manner that is itself known, e.g., by means ofconventional mixing, dissolving, granulating, dragee-making, levigating,emulsifying, encapsulating, entrapping or tabletting processes.

[0094] Pharmaceutical compositions for use in accordance with thepresent invention thus may be formulated in conventional manner usingone or more physiologically acceptable carriers comprising excipientsand auxiliaries which facilitate processing of the active compounds intopreparations which can be used pharmaceutically. Proper formulation isdependent upon the route of administration chosen. Any of the well-knowntechniques, carriers, and excipients may be used as suitable and asunderstood in the art; e.g., in Remington's Pharmaceutical Sciences,above.

[0095] For injection, the agents of the invention may be formulated inaqueous solutions, preferably in physiologically compatible buffers suchas Hanks's solution, Ringer's solution, or physiological saline buffer.For transmucosal administration, penetrants appropriate to the barrierto be permeated are used in the formulation. Such penetrants aregenerally known in the art.

[0096] For oral administration, the compounds can be formulated readilyby combining the active compounds with pharmaceutically acceptablecarriers well known in the art. Such carriers enable the compounds ofthe invention to be formulated as tablets, pills, dragees, capsules,liquids, gels, syrups, slurries, suspensions and the like, for oralingestion by a patient to be treated. Pharmaceutical preparations fororal use can be obtained by mixing one or more solid excipient withpharmaceutical combination of the invention, optionally grinding theresulting mixture, and processing the mixture of granules, after addingsuitable auxiliaries, if desired, to obtain tablets or dragee cores.Suitable excipients are, in particular, fillers such as sugars,including lactose, sucrose, mannitol, or sorbitol; cellulosepreparations such as, for example, maize starch, wheat starch, ricestarch, potato starch, gelatin, gum tragacanth, methyl cellulose,hydroxypropylmethyl-cellulose, sodium carboxymethylcellulose, and/orpolyvinylpyrrolidone (PVP). If desired, disintegrating agents may beadded, such as the cross-linked polyvinyl pyrrolidone, agar, or alginicacid or a salt thereof such as sodium alginate.

[0097] Dragee cores are provided with suitable coatings. For thispurpose, concentrated sugar solutions may be used, which may optionallycontain gum arabic, talc, polyvinyl pyrrolidone, carbopol gel,polyethylene glycol, and/or titanium dioxide, lacquer solutions, andsuitable organic solvents or solvent mixtures. Dyestuffs or pigments maybe added to the tablets or dragee coatings for identification or tocharacterize different combinations of active compound doses.

[0098] Pharmaceutical preparations which can be used orally includepush-fit capsules made of gelatin, as well as soft, sealed capsules madeof gelatin and a plasticizer, such as glycerol or sorbitol. The push-fitcapsules can contain the active ingredients in admixture with fillersuch as lactose, binders such as starches, and/or lubricants such astalc or magnesium stearate and, optionally, stabilizers. In softcapsules, the active compounds may be dissolved or suspended in suitableliquids, such as fatty oils, liquid paraffin, or liquid polyethyleneglycols. In addition, stabilizers may be added. All formulations fororal administration should be in dosages suitable for suchadministration.

[0099] For buccal administration, the compositions may take the form oftablets or lozenges formulated in conventional manner.

[0100] For administration by inhalation, the compounds for use accordingto the present invention are conveniently delivered in the form of anaerosol spray presentation from pressurized packs or a nebulizer, withthe use of a suitable propellant, e.g., dichlorodifluoromethane,trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide orother suitable gas. In the case of a pressurized aerosol the dosage unitmay be determined by providing a valve to deliver a metered amount.Capsules and cartridges of, e.g., gelatin for use in an inhaler orinsufflator may be formulated containing a powder mix of the compoundand a suitable powder base such as lactose or starch.

[0101] The compounds may be formulated for parenteral administration byinjection, e.g., by bolus injection or continuous infusion. Formulationsfor injection may be presented in unit dosage form, e.g., in ampoules orin multi-dose containers, with an added preservative. The compositionsmay take such forms as suspensions, solutions or emulsions in oily oraqueous vehicles, and may contain formulatory agents such as suspending,stabilizing and/or dispersing agents.

[0102] Pharmaceutical formulations for parenteral administration includeaqueous solutions of the active compounds in water-soluble form.Additionally, suspensions of the active compounds may be prepared asappropriate oily injection suspensions. Suitable lipophilic solvents orvehicles include fatty oils such as sesame oil, or synthetic fatty acidesters, such as ethyl oleate or triglycerides, or liposomes. Aqueousinjection suspensions may contain substances which increase theviscosity of the suspension, such as sodium carboxymethyl cellulose,sorbitol, or dextran. Optionally, the suspension may also containsuitable stabilizers or agents which increase the solubility of thecompounds to allow for the preparation of highly concentrated solutions.

[0103] Alternatively, the active ingredient may be in powder form forconstitution with a suitable vehicle, e.g., sterile pyrogen-free water,before use.

[0104] The compounds may also be formulated in rectal compositions suchas suppositories or retention enemas, e.g., containing conventionalsuppository bases such as cocoa butter or other glycerides.

[0105] In addition to the formulations described previously, thecompounds may also be formulated as a depot preparation. Such longacting formulations may be administered by implantation (for examplesubcutaneously or intramuscularly) or by intramuscular injection. Thus,for example, the compounds may be formulated with suitable polymeric orhydrophobic materials (for example as an emulsion in an acceptable oil)or ion exchange resins, or as sparingly soluble derivatives, forexample, as a sparingly soluble salt.

[0106] A pharmaceutical carrier for the hydrophobic compounds of theinvention is a cosolvent system comprising benzyl alcohol, a nonpolarsurfactant, a water-miscible organic polymer, and an aqueous phase. Acommon cosolvent system used is the VPD co-solvent system, which is asolution of 3% w/v benzyl alcohol, 8% w/v of the nonpolar surfactantPolysorbate 80™, and 65% w/v polyethylene glycol 300, made up to volumein absolute ethanol. Naturally, the proportions of a co-solvent systemmay be varied considerably without destroying its solubility andtoxicity characteristics. Furthermore, the identity of the co-solventcomponents may be varied: for example, other low-toxicity nonpolarsurfactants may be used instead of POLYSORBATE 80™; the fraction size ofpolyethylene glycol may be varied; other biocompatible polymers mayreplace polyethylene glycol, e.g., polyvinyl pyrrolidone; and othersugars or polysaccharides may substitute for dextrose.

[0107] Alternatively, other delivery systems for hydrophobicpharmaceutical compounds may be employed. Liposomes and emulsions arewell known examples of delivery vehicles or carriers for hydrophobicdrugs. Certain organic solvents such as dimethylsulfoxide also may beemployed, although usually at the cost of greater toxicity.Additionally, the compounds may be delivered using a sustained-releasesystem, such as semipermeable matrices of solid hydrophobic polymerscontaining the therapeutic agent. Various sustained-release materialshave been established and are well known by those skilled in the art.Sustained-release capsules may, depending on their chemical nature,release the compounds for a few weeks up to over 100 days. Depending onthe chemical nature and the biological stability of the therapeuticreagent, additional strategies for protein stabilization may beemployed.

[0108] Many of the compounds used in the pharmaceutical combinations ofthe invention may be provided as salts with pharmaceutically compatiblecounterions. Pharmaceutically compatible salts may be formed with manyacids, including but not limited to hydrochloric, sulfuric, acetic,lactic, tartaric, malic, succinic, etc. Salts tend to be more soluble inaqueous or other protonic solvents than are the corresponding free acidor base forms.

[0109] Pharmaceutical compositions suitable for use in the presentinvention include compositions where the active ingredients arecontained in an amount effective to achieve its intended purpose. Morespecifically, a therapeutically effective amount means an amount ofcompound effective to prevent, alleviate or ameliorate symptoms ofdisease or prolong the survival of the subject being treated.Determination of a therapeutically effective amount is well within thecapability of those skilled in the art, especially in light of thedetailed disclosure provided herein.

[0110] The exact formulation, route of administration and dosage for thepharmaceutical compositions of the present invention can be chosen bythe individual physician in view of the patient's condition. (See e.g.,Fingl et al. 1975, in “The Pharmacological Basis of Therapeutics”, Ch. 1p. 1). Typically, the dose range of the composition administered to thepatient can be from about 0.5 to 1000 mg/kg of the patient's bodyweight. The dosage may be a single one or a series of two or more givenin the course of one or more days, as is needed by the patient. Notethat for almost all of the specific compounds mentioned in the presentdisclosure, human dosages for treatment of at least some condition havebeen established. Thus, in most instances, the present invention willuse those same dosages, or dosages that are between about 0.1% and 500%,more preferably between about 25% and 250% of the established humandosage. Where no human dosage is established, as will be the case fornewly-discovered pharmaceutical compounds, a suitable human dosage canbe inferred from ED₅₀ or ID₅₀ values, or other appropriate valuesderived from in vitro or in vivo studies, as qualified by toxicitystudies and efficacy studies in animals.

[0111] Although the exact dosage will be determined on a drug-by-drugbasis, in most cases, some generalizations regarding the dosage can bemade. The daily dosage regimen for an adult human patient may be, forexample, an oral dose of between 0.1 mg and 500 mg of each ingredient,preferably between 1 mg and 250 mg, e.g. 5 to 200 mg or an intravenous,subcutaneous, or intramuscular dose of each ingredient between 0.01 mgand 100 mg, preferably between 0.1 mg and 60 mg, e.g. 1 to 40 mg of eachingredient of the pharmaceutical compositions of the present inventionor a pharmaceutically acceptable salt thereof calculated as the freebase, the composition being administered 1 to 4 times per day.Alternatively the compositions of the invention may be administered bycontinuous intravenous infusion, preferably at a dose of each ingredientup to 400 mg per day. Thus, the total daily dosage by oraladministration of each ingredient will typically be in the range 1 to2000 mg and the total daily dosage by parenteral administration willtypically be in the range 0.1 to 400 mg. Suitably the compounds will beadministered for a period of continuous therapy, for example for a weekor more, or for months or years.

[0112] Dosage amount and interval may be adjusted individually toprovide plasma levels of the active moiety which are sufficient tomaintain the modulating effects, or minimal effective concentration(MEC). The MEC will vary for each compound but can be estimated from invitro data. Dosages necessary to achieve the MEC will depend onindividual characteristics and route of administration. However, HPLCassays or bioassays can be used to determine plasma concentrations.

[0113] Dosage intervals can also be determined using MEC value.Compositions should be administered using a regimen which maintainsplasma levels above the MEC for 10-90% of the time, preferably between30-90% and most preferably between 50-90%.

[0114] In cases of local administration or selective uptake, theeffective local concentration of the drug may not be related to plasmaconcentration.

[0115] The amount of composition administered will, of course, bedependent on the subject being treated, on the subject's weight, theseverity of the affliction, the manner of administration and thejudgment of the prescribing physician.

[0116] The compositions may, if desired, be presented in a pack ordispenser device which may contain one or more unit dosage formscontaining the active ingredient. The pack may for example comprisemetal or plastic foil, such as a blister pack. The pack or dispenserdevice may be accompanied by instructions for administration. The packor dispenser may also be accompanied with a notice associated with thecontainer in form prescribed by a governmental agency regulating themanufacture, use, or sale of pharmaceuticals, which notice is reflectiveof approval by the agency of the form of the drug for human orveterinary administration. Such notice, for example, may be the labelingapproved by the U.S. Food and Drug Administration for prescriptiondrugs, or the approved product insert. Compositions comprising acompound of the invention formulated in a compatible pharmaceuticalcarrier may also be prepared, placed in an appropriate container, andlabeled for treatment of an indicated condition.

[0117] It will be understood by those of skill in the art that numerousand various modifications can be made without departing from the spiritof the present invention. Therefore, it should be clearly understoodthat the forms of the present invention are illustrative only and arenot intended to limit the scope of the present invention.

[0118] Some Embodiments of the Invention

[0119] Some of the embodiments of the present invention are as follows:

[0120] In the first embodiment, the invention relates to a compositionfor affecting weight loss comprising a first compound and a secondcompound, wherein said first compound is an opioid antagonist and saidsecond compound causes increased agonism of a melanocortin 3 receptor(MC3-R) or a melanocortin 4 receptor (MC4-R) compared to normalphysiological conditions.

[0121] In the second embodiment, the invention relates to thecomposition of the first embodiment, wherein said opioid antagonistantagonizes an opioid receptor in a mammal.

[0122] In the third embodiment, the invention relates to the compositionof the second embodiment, wherein said opioid receptor is selected froma μ-opioid receptor (MOP-R), a η-opioid receptor, and a δ-opioidreceptor.

[0123] In the fourth embodiment, the invention relates to thecomposition of the second embodiment, wherein said opioid antagonistantagonizes a μ-opioid receptor (MOP-R) in a mammal.

[0124] In the fifth embodiment, the invention relates to the compositionof the first embodiment, wherein said opioid antagonist is selected fromthe group consisting of alvimopan, norbinaltorphimine, nalmefene,naloxone, naltrexone, methylnaltrexone, and nalorphine, andpharmaceutically acceptable salts or prodrugs thereof.

[0125] In the sixth embodiment, the invention relates to the compositionof the first embodiment, wherein said opioid antagonist is a partialopioid agonist.

[0126] In the seventh embodiment, the invention relates to thecomposition of the sixth embodiment, wherein said partial opioid agonistis selected from the group consisting of pentacozine, buprenorphine,nalorphine, propiram, and lofexidine.

[0127] In the eighth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compoundtriggers the release of α-melanocyte stimulating hormone (α-MSH).

[0128] In the ninth embodiment, the invention relates to the compositionof the eighth embodiment, wherein said second compound increases theextracellular serotonin concentrations in the hypothalamus.

[0129] In the tenth embodiment, the invention relates to the compositionof the ninth embodiment, wherein said second compound is selected fromthe group consisting of a selective serotonin reuptake inhibitor (SSRI),a serotonin 2C agonist, and a serotonin 1B agonist.

[0130] In the eleventh embodiment, the invention relates to thecomposition of the tenth embodiment, wherein said second compound isselected from the group consisting of fluoxetine, fluvoxamine,sertraline, paroxetine, citalopram, escitalopram, sibutramine,duloxetine, and venlafaxine, and pharmaceutically acceptable salts orprodrugs thereof.

[0131] In the twelfth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compoundsuppresses the expression of the AgRP gene or the production or releaseof agouti-related protein (AgRP).

[0132] In the thirteenth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compoundsuppresses the activity of neurons that express AgRP.

[0133] In the fourteenth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compoundsuppresses the expression of the NPY gene or the production or releaseof neuropeptide Y (NPY).

[0134] In the fifteenth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compoundsuppresses the activity of neurons that express NPY.

[0135] In the sixteenth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compound isselected from the group consisting of NPY Y1 receptor antagonists,ghrelin antagonists, and leptin.

[0136] In the seventeenth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compoundagonizes NPY Y2 receptor.

[0137] In the eighteenth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compound isselected from the group consisting of a γ-amino butyric acid (GABA)inhibitor, a GABA receptor antagonist, and a GABA channel antagonist.

[0138] In the nineteenth embodiment, the invention relates to thecomposition of the eighteenth embodiment, wherein said GABA inhibitor isa 5-HT1b agonist, which may be selected from sumatriptan, almotriptan,naratriptan, frovatriptan, rizatriptan, zomitriptan, and elitriptan.

[0139] In the twentieth embodiment, the invention relates to thecomposition of the eighteenth embodiment, wherein said GABA inhibitorsuppresses the expression of the AgRP gene.

[0140] In the twenty first embodiment, the invention relates to thecomposition of the eighteenth embodiment, wherein said GABA inhibitorsuppresses the production or release of AgRP.

[0141] In the twenty second embodiment, the invention relates to thecomposition of the eighteenth embodiment, wherein said GABA inhibitorincreases the expression of the POMC gene.

[0142] In the twenty third embodiment, the invention relates to thecomposition of the eighteenth embodiment, wherein said GABA inhibitorincreases the production or release of α-MSH from pro-opiomelanocortin(POMC) neurons.

[0143] In the twenty fourth embodiment, the invention relates to thecomposition of the eighteenth embodiment, wherein said GABA inhibitorincreases the activity of POMC expressing neurons.

[0144] In the twenty fifth embodiment, the invention relates to thecomposition of the eighteenth embodiment, wherein the GABA inhibitor istopiramate.

[0145] In the twenty sixth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compound is adopamine reuptake inhibitor.

[0146] In the twenty seventh embodiment, the invention relates to thecomposition of the twenty sixth embodiment, wherein said dopaminereuptake inhibitor is phentermine.

[0147] In the twenty eighth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compound is anorepinephrine reuptake inhibitor.

[0148] In the twenty ninth embodiment, the invention relates to thecomposition of the twenty eighth embodiment, wherein said norepinephrinereuptake inhibitor is selected from bupropion, thionisoxetine, andreboxetine.

[0149] In the thirtieth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compound is adopamine agonist.

[0150] In the thirty first embodiment, the invention relates to thecomposition of the thirtieth embodiment, wherein said dopamine agonistis selected from the group consisting of cabergoline, amantadine,lisuride, pergolide, ropinirole, pramipexole, and bromocriptine.

[0151] In the thirty second embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compound is anorepinephrine releaser.

[0152] In the thirty third embodiment, the invention relates to thecomposition of the thirty second embodiment, wherein said norepinephrinereleaser is diethylpropion.

[0153] In the thirty fourth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compound is acombination of a dopamine reuptake inhibitor and a norepinephrinereuptake inhibitor.

[0154] In the thirty fifth embodiment, the invention relates to thecomposition of the thirty fourth embodiment, wherein said secondcompound is selected from bupropion and mazindol.

[0155] In the thirty sixth embodiment, the invention relates to thecomposition of the first embodiment, wherein said second compound is acombination of a SSRI and a norepinephrine reuptake inhibitor.

[0156] In the thirty seventh embodiment, the invention relates to thecomposition of the thirty sixth embodiment, wherein said second compoundis selected from sibutramine, venlafaxine, and duloxetine.

[0157] In the thirty eighth embodiment, the invention relates to thecomposition of the first embodiment, wherein said first compound isnaltrexone and said second compound is fluoxetine.

[0158] In the thirty ninth embodiment, the invention relates to thecomposition of the thirty eighth embodiment, wherein the naltrexone isin a time-release formulation whereas the fluoxetine is in an immediaterelease formulation.

[0159] In the fortieth embodiment, the invention relates to a method ofaffecting weight loss, comprising identifying an individual in needthereof and treating that individual to antagonize opioid receptoractivity and to enhance α-MSH activity.

[0160] In the forty first embodiment, the invention relates to themethod of the fortieth embodiment, wherein said individual has a bodymass index greater than 25.

[0161] In the forty second embodiment, the invention relates to themethod of the fortieth embodiment, wherein opioid receptor activity isantagonized by administering an opioid receptor antagonist.

[0162] In the forty third embodiment, the invention relates to themethod of the forty second embodiment, wherein the opioid receptorantagonist is a MOP receptor antagonist.

[0163] In the forty fourth embodiment, the invention relates to themethod of the fortieth embodiment, wherein the opioid receptorantagonist is selected from alvimopan, norbinaltorphimine, nalmefene,naloxone, naltrexone, methylnaltrexone, and nalorphine, andpharmaceutically acceptable salts or prodrugs thereof.

[0164] In the forty fifth embodiment, the invention relates to themethod of the forty second embodiment, wherein said opioid receptorantagonist is a partial opioid agonist.

[0165] In the forty sixth embodiment, the invention relates to themethod of the forty fifth embodiment, wherein said partial opioidagonist is selected from the group consisting of pentacozine,buprenorphine, nalorphine, propiram, and lofexidine.

[0166] In the forty seventh embodiment, the invention relates to themethod of the fortieth embodiment through the forty fifth embodiment,wherein α-MSH activity is enhanced by administering a compound, whereinsaid compound triggers release of α-MSH or increases the activity ofneurons that express α-MSH.

[0167] In the forty eighth embodiment, the invention relates to themethod of the forty seventh embodiment, wherein said compound is aselective serotonin reuptake inhibitor (SSRI) or a specific 5-HTreceptor agonist.

[0168] In the forty ninth embodiment, the invention relates to themethod of the forty eighth embodiment, wherein said 5-HT receptor isselected from 5-HT1b receptor and 5-HT2c receptor.

[0169] In the fiftieth embodiment, the invention relates to the methodof the forty eighth embodiment, wherein said SSRI is selected fromfluoxetine, fluvoxamine, sertraline, paroxetine, citalopram,escitalopram, sibutramine, duloxetine, and venlafaxine, andpharmaceutically acceptable salts or prodrugs thereof.

[0170] In the fifty first embodiment, the invention relates to themethod of the forty seventh embodiment, wherein said compound is aγ-amino butyric acid (GABA) inhibitor.

[0171] In the fifty second embodiment, the invention relates to themethod of the fifty first embodiment, wherein said GABA inhibitor is a5-HT1b receptor agonist.

[0172] In the fifty third embodiment, the invention relates to themethod of the fifty first embodiment, wherein said GABA inhibitorsuppresses the expression of the AgRP gene.

[0173] In the fifty fourth embodiment, the invention relates to themethod of the fifty first embodiment, wherein said GABA inhibitorsuppresses the production or release of AgRP.

[0174] In the fifty fifth embodiment, the invention relates to themethod of the forty eighth embodiment, wherein said 5-HT agonistsinhibits the NPY/AgRP/GABA neurons.

[0175] In the fifty sixth embodiment, the invention relates to themethod of the fifty first embodiment, wherein said GABA inhibitorsuppresses the activity of neurons that express AgRP.

[0176] In the fifty seventh embodiment, the invention relates to themethod of the fifty first embodiment, wherein said GABA inhibitor istopiramate.

[0177] In the fifty eighth embodiment, the invention relates to themethod of the forty seventh embodiment, wherein said compound isselected from the group consisting of a dopamine reuptake inhibitor, anorepinephrine reuptake inhibitor, a dopamine agonist, a norepinephrinereleaser, a combination of a dopamine reuptake inhibitor and anorepinephrine reuptake inhibitor, and a combination of a SSRI and anorepinephrine reuptake inhibitor.

[0178] In the fifty ninth embodiment, the invention relates to themethod of the fifty eighth embodiment, wherein said compound is notphentermine.

[0179] In the sixtieth embodiment, the invention relates to the methodof the fortieth embodiment, with the proviso that the individual is notsuffering from Prader-Willi syndrome.

[0180] In the sixty first embodiment, the invention relates to themethod of the fortieth embodiment, with the proviso that if the opioidreceptor is antagonized using naltrexone, then release of α-MSH is notstimulated with fluoxetine.

[0181] In the sixty second embodiment, the invention relates to themethod of the fortieth embodiment, wherein said treating step comprisesadministering to said individual a first compound and a second compound,wherein said first compound is an opioid antagonist and said secondcompound enhances α-MSH activity.

[0182] In the sixty third embodiment, the invention relates to themethod of the sixty second embodiment, wherein said first compound andsaid second compound are administered nearly simultaneously.

[0183] In the sixty fourth embodiment, the invention relates to themethod of the sixty third embodiment, wherein said first compound isadministered prior to said second compound.

[0184] In the sixty fifth embodiment, the invention relates to themethod of the sixty fourth embodiment, wherein said first compound isadministered subsequent to said second compound.

[0185] In the sixty sixth embodiment, the invention relates to a methodof increasing satiety in an individual comprising identifying anindividual in need thereof and treating that individual to antagonizeopioid receptor activity and to enhance α-MSH activity.

[0186] In the sixty seventh embodiment, the invention relates to themethod of the sixty sixth embodiment, wherein said treating stepcomprises administering to said individual a first compound and a secondcompound, wherein said first compound is an opioid antagonist and saidsecond compound enhances α-MSH activity.

[0187] In the sixty eighth embodiment, the invention relates to themethod of the sixty seventh embodiment, wherein said first compound andsaid second compound are administered nearly simultaneously.

[0188] In the sixty ninth embodiment, the invention relates to themethod of the sixty seventh embodiment, wherein said first compound isadministered prior to said second compound.

[0189] In the seventieth embodiment, the invention relates to the methodof the sixty seventh embodiment, wherein said first compound isadministered subsequent to said second compound.

[0190] In the seventy first embodiment, the invention relates to amethod of increasing energy expenditure in an individual comprisingidentifying an individual in need thereof and treating that individualto antagonize opioid receptor activity and to enhance α-MSH activity.

[0191] In the seventy second embodiment, the invention relates to themethod of the seventy first embodiment, wherein said treating stepcomprises administering to said individual a first compound and a secondcompound, wherein said first compound is an opioid antagonist and saidsecond compound enhances α-MSH activity.

[0192] In the seventy third embodiment, the invention relates to themethod of the seventy second embodiment, wherein said first compound andsaid second compound are administered nearly simultaneously.

[0193] In the seventy fourth embodiment, the invention relates to themethod of the seventy second embodiment, wherein said first compound isadministered prior to said second compound.

[0194] In the seventy fifth embodiment, the invention relates to themethod of the seventy second embodiment, wherein said first compound isadministered subsequent to said second compound.

[0195] In the seventy sixth embodiment, the invention relates to amethod of suppressing the appetite of an individual comprisingidentifying an individual in need thereof and treating that individualto antagonize opioid receptor activity and to enhance α-MSH activity.

[0196] In the seventy seventh embodiment, the invention relates to themethod of the seventy sixth embodiment, wherein said treating stepcomprises administering to said individual a first compound and a secondcompound, wherein said first compound is an opioid antagonist and saidsecond compound enhances α-MSH activity.

[0197] In the seventy eighth embodiment, the invention relates to themethod of the seventy seventh embodiment, wherein said first compoundand said second compound are administered nearly simultaneously.

[0198] In the seventy ninth embodiment, the invention relates to themethod of the seventy seventh embodiment, wherein said first compound isadministered prior to said second compound.

[0199] In the eightieth embodiment, the invention relates to the methodof the seventy seventh embodiment, wherein said first compound isadministered subsequent to said second compound.

[0200] In the eighty first embodiment, the invention relates to a methodof affecting weight loss in an individual comprising identifying anindividual in need thereof and treating that individual with acombination of naltrexone and fluoxetine,

[0201] provided that the individual does not suffer from Prader-Willisyndrome or binge eating disorder.

[0202] In the eighty second embodiment, the invention relates to themethod of the eighty first embodiment, wherein the individual has a BMIgreater than 30.

[0203] In the eighty third embodiment, the invention relates to themethod of the eighty first embodiment, wherein the individual has a BMIgreater than 25.

[0204] In the eighty fourth embodiment, the invention relates to themethod of the eighty first embodiment, wherein the naltrexone is in atime-release formulation whereas the fluoxetine is in an immediaterelease formulation.

[0205] In the eighty fifth embodiment, the invention relates to themethod of the eighty fourth embodiment, wherein the plasma concentrationlevel of both naltrexone and fluoxetine follow a similar concentrationprofile.

[0206] In the eighty sixth embodiment, the invention relates to themethod of the eighty fourth embodiment, wherein the naltrexone and thefluoxetine are administered substantially simultaneously.

[0207] In the eighty seventh embodiment, the invention relates to themethod of the eighty fourth embodiment, wherein the naltrexone isadministered prior to the fluoxetine.

[0208] In the eighty eighth embodiment, the invention relates to themethod of the eighty fourth embodiment, wherein the naltrexone isadministered subsequent to the fluoxetine.

EXAMPLES

[0209] The examples below are non-limiting and are merely representativeof various aspects of the invention.

Example 1 Combination of Fluoxetine and Naltrexone

[0210] Individuals having a BMI of greater than 25 are identified. Eachindividual is instructed to take one 20 mg tablet of fluoxetine(PROZAC®) on a daily basis, in addition to one 50 mg tablet ofnaltrexone on a daily basis.

[0211] The individuals are monitored for a period of months. It isrecommended that the dosage be adjusted so that each individual losesweight at a rate of 10% of initial weight every 6 months. However, therate of weigh loss for each individual may be adjusted by the treatingphysician based on the individual's particular needs.

[0212] If the initial dosage is not effective, then the fluoxetinedosage can be increased by 20 mg per day, though never exceeding 80 mgtotal per day. If the initial dosage results in a more rapid weight lossthan the above rate, the dosage of each of fluoxetine or naltrexone canbe reduced.

[0213] Fluoxetine has a physiological half life of about 9 hours,whereas that of naltrexone is about 1.5 hours. Thus, in some cases, itis beneficial to administer one dose of fluoxetine per day inconjunction with two or three or more doses of naltrexone throughout theday. Naltrexone may also be in a time-release formulation where the doseis administered once a day, but naltrexone gradually enters the bloodstream throughout the day, or in the course of a 12 hour period.

Example 2 Combination of Fluoxetine and Nalmefene

[0214] Individuals having a BMI of greater than 25 are identified. Eachindividual is instructed to take one 20 mg tablet of fluoxetine(PROZAC®) on a daily basis. In addition, each individual is injectedwith 1 mL of a solution of 100 μg of nalmefene in 1 mL of saline,intravenously, intramuscularly, or subcutaneously.

[0215] The individuals are monitored for a period of months. It isrecommended that the dosage be adjusted so that each individual losesweight at a rate of 10% of initial weight every 6 months. However, therate of weigh loss for each individual may be adjusted by the treatingphysician based on the individual's particular needs.

[0216] If the initial dosage is not effective, then the fluoxetinedosage can be increased by 20 mg per day, though never exceeding 80 mgtotal per day. In addition, the dosage of nalmefene may be increased upto 2 mL of a solution of 1 mg of nalmefene in 1 mL of saline. If theinitial dosage results in a more rapid weight loss than the above rate,the dosage of each of fluoxetine or nalmefene can be reduced.

Example 3 Combination of Fluoxetine and Naloxone

[0217] Individuals having a BMI of greater than 25 are identified. Eachindividual is instructed to take one 20 mg tablet of fluoxetine(PROZAC®) on a daily basis. In addition, each individual is injectedwith 1 mL of a solution of 400 μg of naloxone in 1 mL of saline,intravenously, intramuscularly, or subcutaneously.

[0218] The individuals are monitored for a period of months. It isrecommended that the dosage be adjusted so that each individual losesweight at a rate of 10% of initial weight every 6 months. However, therate of weigh loss for each individual may be adjusted by the treatingphysician based on the individual's particular needs.

[0219] If the initial dosage is not effective, then the fluoxetinedosage can be increased by 20 mg per day, though never exceeding 80 mgtotal per day. If the initial dosage results in a more rapid weight lossthan the above rate, the dosage of each of fluoxetine or nalmefene canbe reduced.

Example 4 Combination of Opioid Antagonist and Sibutramine

[0220] Individuals having a BMI of greater than 25 are identified. Eachindividual is instructed to take nalmefene, naltrexone, or naloxone inthe dosage set forth in Examples 1-3. In addition, each individual isinstructed to take 10 mg of sibutramine orally once a day.

[0221] The individuals are monitored for a period of months. It isrecommended that the dosage be adjusted so that each individual losesweight at a rate of 10% of initial weight every 6 months. However, therate of weigh loss for each individual may be adjusted by the treatingphysician based on the individual's particular needs.

[0222] If the initial dosage is not effective, then the sibutraminedosage can be increased 15 mg per day. Dosages of sibutramine in excessof 15 mg per day are not recommended. If the initial dosage results in amore rapid weight loss than the above rate, the dosage of each ofsibutramine, nalmefene, naltrexone, or naloxone can be reduced.

Example 5 Combination of Opioid Antagonist and Bupropion

[0223] Individuals having a BMI of greater than 25 are identified. Eachindividual is instructed to take nalmefene, naltrexone, or naloxone inthe dosage set forth in Examples 1-3. In addition, each individual isinstructed to take bupropion. The usual adult does is 300 mg per day,given three times daily. Dosing should begin at 200 mg per day, given as100 mg twice daily. Based on clinical response, this dose may beincreased to 300 mg per day, given as 100 mg three times daily. Nosingle dose is to exceed 150 mg.

[0224] The individuals are monitored for a period of months. It isrecommended that the dosage be adjusted so that each individual losesweight at a rate of 10% of initial weight every 6 months. However, therate of weigh loss for each individual may be adjusted by the treatingphysician based on the individual's particular needs.

Example 6 Combination of Opioid Antagonist and Phentermine

[0225] Individuals having a BMI of greater than 25 are identified. Eachindividual is instructed to take nalmefene, naltrexone, or naloxone inthe dosage set forth in Examples 1-3. In addition, each individual isinstructed to take 37.5 mg of phentermine orally once a day.

[0226] The individuals are monitored for a period of months. It isrecommended that the dosage be adjusted so that each individual losesweight at a rate of 10% of initial weight every 6 months. However, therate of weigh loss for each individual may be adjusted by the treatingphysician based on the individual's particular needs.

Example 7 Combinations with Naltrexone

[0227] In a multicenter, randomized, blinded, placebo-controlledclinical trial with 6 groups, the following drug combinations aretested:

[0228] Group 1: Fluoxetine 60 mg po QD plus Naltrexone 50 mg po QD

[0229] Group 2: Fluoxetine 60 mg po QD plus N-placebo po QD

[0230] Group 3: Bupropion-SR 150 mg po BID plus Naltrexone 50 mg po QD

[0231] Group 4: Bupropion-SR 150 mg po BID plus N-placebo po QD

[0232] Group 5: P-placebo po BID plus Naltrexone 50 mg po QD

[0233] Group 6: P-placebo po BID plus N-placebo po QD

[0234] In any of the above groups, the dosage of fluoxetine may be inthe range between 6 mg and 60 mg, for example, 6 mg, 10 mg, 12 mg, 18mg, 20 mg, 24 mg, 30 mg, 36 mg, 40 mg, 42 mg, 45 mg, 48 mg, 54 mg, and60 mg. Bupropion may be administered in doses in the range between 30 mgand 300 mg, for example, 30 mg, 40 mg, 50 mg, 60 mg, 70 mg, 80 mg, 90mg, 100 mg, 110 mg, 120 mg, 130 mg, 140 mg, 150 mg, 160 mg, 170 mg, 180mg, 190 mg, 200 mg, 210 mg, 220 mg, 230 mg, 240 mg, 250 mg, 260 mg, 270mg, 280 mg, 290 mg, and 300 mg. Naltrexone may be administered in dosesin the range between 5 mg and 50 mg, for example, 5 mg, 10 mg, 15 mg, 20mg, 25 mg, 30 mg, 35 mg, 40 mg, 45 mg, and 50 mg.

[0235] Subjects are evaluated as out-patients during this study. Allsubjects in this trial receive diet instruction, behavior modificationadvice and instruction to increase their activity, a regimen shown togive weight loss. Subjects are randomized to receive study drugs invarious combinations.

[0236] Subjects in groups 5 and 6 cross-over to treatment withfluoxetine plus naltrexone or bupropion SR plus naltrexone after week 16for the extension treatment period which provide additional data onsafety of the combination therapies.

[0237] The primary endpoint is percent and absolute change from baselinein body weight at 16 weeks. Secondary endpoints include weight loss at24, 36, and 48 weeks, number and proportion of subjects who achieve atleast a 5% weight loss and a 10% weight loss (responder analysis),changes in obesity-associated cardiovascular risk factors (totalcholesterol, LDL cholesterol, HDL cholesterol, triglycerides, glucoseand insulin) and waist circumference, and safety and tolerability.Adverse events, laboratory parameters, vital signs, and the HospitalAnxiety and Depression (HAD) Scale are used to monitor safety andtolerability.

Example 8 Dose-Response Experiments

[0238] Seventy, four week old, male C57/B16J⁻ mice (Jackson Laboratory),22-30 g were sham injected daily with 0.1 mL 0.9% saline (pH 7.4) for 1week prior to the experiments. Animals were weighed and randomized to 1of 7 weight-matched dose groups (0, 1.5, 3, 5.5, 10, 18, and 30 mg/kg;n=10/group for fluoxetine; 0, 1.5, 3, 5.5, 10, 18, and 30 mg/kg;n=3/group for naltrexone) the day before experiments began. Food wasremoved between 4:30-5:30 pm the day before the experiment. Animalsreceived a 0.3 mL bolus (fluoxetine) or 0.1 mL bolus (naltrexone)intraperitoneal injection between 9-10:30 am, and food was providedimmediately following injection. 3 animals/group received injections oneach testing day (i.e., 3 runs of 3/group; 1 run of 1/group). Food wasweighed 1, 2, 4, 8, and 24 h post-injection. Cumulative food intake±SEMwas calculated and analyzed using Prizm. Doses were log transformed andfit to a sigmoidal curve, food intake was expressed as a proportion ofthe food intake in saline treated animals. From the curve, the EC₅₀ ateach time point for each drug was determined.

[0239] Similar procedures as described above were followed using AM251and nalmefene, fluvoxamine and nalmefene, and bupropion and naltrexone.

[0240] The results are set forth in the table below: Hour 1 Hour 2 Hour4 Hour 8 Hour 8 SEM SEM SEM SEM SEM MEAN (±) MEAN (±) MEAN (±) MEAN (±)MEAN (±) Saline 1.00 0.0690 1.00 0.062 1.00 0.047 1.00 0.052 1.00 0.042AM 251 0.97 0.086 0.85 0.060 0.88 0.057 0.90 0.036 0.99 0.054Fluvoxamine 0.77 0.058 0.85 0.056 0.95 0.044 0.91 0.034 0.92 0.054Nalmefene 0.0083 0.0062 0.11 0.061 0.57 0.11 0.81 0.068 0.98 0.027 AM251 + 0.010 0.010 0.075 0.055 0.30 0.1 0.62 0.042 0.90 0.021 NalmefeneFluvoxamine + 0.0041 0.0041 0.019 0.012 0.42 0.087 0.79 0.026 0.99 0.031Nalmefene Bupropion 0.32 0.044 0.64 0.049 0.97 0.048 0.96 0.036 0.990.020 Naltrexone 0.41 0.040 0.77 0.060 0.99 0.062 1.1 0.048 0.98 0.030Naltrexone + 0.042 0.0068 0.34 0.10 0.89 0.055 0.97 0.044 0.95 0.028Bupropion Naltrexone 0.30 0.10 0.56 0.050 0.83 0.10 0.98 0.19 1.01 0.22Fluoxetine 0.36 0.030 0.57 0.13 0.68 0.15 0.76 0.21 1.05 0.22Naltrexone + 0.070 0.030 0.26 0.060 0.72 0.11 0.95 0.18 1.04 0.26Fluoxetine

Example 9 Electrophysiology Data

[0241] To test the hypothesis that drugs selectively activate POMCneurons, we used a strain of transgenic mice expressing greenfluorescent protein (EGFP, Clontech), under the transcriptional controlof mouse Pomc genomic sequences that include a region located between−13 kb and −2 kb required for accurate neuronal expression Bright greenfluorescence (509 nm) was seen in the two CNS regions where POMC isproduced: the ARC and the nucleus of the solitary tract. Underultraviolet (450-480 nm) excitation, POMC neurons were clearlydistinguished from adjacent, non-fluorescent neurons visualized underinfrared optics.

[0242] 200 μm thick coronal slices were cut from the ARC of four-weekold male POMC-EGFP mice. Slices were maintained in Krebs solution (NaCl(126 mM), KCl (2.5 mM), MgCl₂ 91.2 mM), CaCl₂.2H₂O (2.4 mM), NaH₂PO₄.H₂O(1.2 mM), NaHCO₃ (21.4 mM), glucose (11.1 mM)) at 35° C. and saturatedwith 95% O₂ and 5% CO₂ for 1 hr prior to recordings. Recordings weremade in Krebs at 35° C. Slices were visualized on an Axioskop FS2 plus(Zeiss) through standard infra red optics and using epifluorescencethrough a FITC (longpass) filter set. POMC-EGFP neurons in hypothalamicslices had a resting membrane potential of −40 to −45 mV and exhibitedfrequent spontaneous action potentials. Cell-attached recordings weremade from fluorescent neurons using an Axopatch 200B amplifier (AxonInstruments) and Clampex 8 (Axon Instruments). Action potentialsfrequencies were determined using an event detection program (MiniAnalysis; Synaptosoft Inc., Decatur, Ga.). Drugs were applied to thebath for 3 min.

[0243] Data were analyzed by determining the average firing rate for 500sec prior to drug addition, and analyzing treatments relative to thisfrequency (that is, firing rates were normalized to the pre-treatmentfrequency). The ratio's listed for the combinations are the ratio of theeffect of naltrexone in combination with the POMC activator, relative tonaltrexone alone (that is the extra effectiveness that naltrexoneconferred to the POMC activator). Also listed are the mean effects ofthe drugs alone. Fenfluramine   2X increase (n = 6) Fenfluramine +Naltrexone 5.2X (n = 8) Fluoxetine   3X (n = 1) Fluoxetine + Naltrexone1.2X (n = 1) Dopamine  11X (n = 9) Dopamine + Naltrexone 1.5X (n = 3)

[0244] Naltrexone alone has a potent (7×) but variable effect. manycells did not respond to naltrexone alone, but gave a significantresponse to combination treatment. Heisler et al. (Science297(5581):609-11 (2002)) show that fenfluramine alone causes a 200%effect.

[0245] The results are set forth in the table below: Drug Dose Effect(%) Drug Dose Effect (%) Ratio Naltrexone 1 μM 29650 Naltrexone + 1 μM +20 μM 15080 0.51 Fenfluramine Naltrexone 1 μM 2200 Naltrexone + 1 μM +20 μM 11440 520 Fenfluramine Naltrexone 1 μM 2500 Naltrexone + 1 μM + 20μM 856 0.34 Fenfluramine Naltrexone 1 μM 417 Naltrexone + 1 μM + 20 μM5700 13.67 Fenfluramine Naltrexone 1 μM 177 Naltrexone + 1 μM + 20 μM430 2.43 Fenfluramine Naltrexone 1 μM 200 Naltrexone + 1 μM + 20 μM 293314.67 Fenfluramine Naltrexone 1 μM 700 Naltrexone + 1 μM + 20 μMFenfluramine Naltrexone 1 μM 900 Naltrexone + 1 μM + 20 μM 1831 2.03Fenfluramine Naltrexone 1 μM 2273 Naltrexone + 1 μM + 20 μM FenfluramineNaltrexone 1 μM 300 Naltrexone + 1 μM + 20 μM 920 3.07 Fenfluramine

What is claimed is:
 1. A composition for affecting weight losscomprising a first compound and a second compound, wherein said firstcompound is an opioid antagonist and said second compound causesincreased agonism of a melanocortin 3 receptor (MC3-R) or a melanocortin4 receptor (MC4-R) compared to normal physiological conditions.
 2. Thecomposition of claim 1, wherein said opioid antagonist antagonizes anopioid receptor selected from a μ-opioid receptor (MOP-R), a η-opioidreceptor, and a δ-opioid receptor.
 3. The composition of claim 1,wherein said opioid antagonist is selected from the group consisting ofalvimopan, norbinaltorphimine, nalmefene, naloxone, naltrexone,methylnaltrexone, and nalorphine, and pharmaceutically acceptable saltsor prodrugs thereof.
 4. The composition of claim 1, wherein said secondcompound triggers the release of α-melanocyte stimulating hormone(α-MSH).
 5. The composition of claim 4, wherein said second compoundincreases the extracellular serotonin concentrations in thehypothalamus.
 6. The composition of claim 5, wherein said secondcompound is selected from the group consisting of a selective serotoninreuptake inhibitor (SSRI), a serotonin 2C agonist, and a serotonin 1Bagonist.
 7. The composition of claim 6, wherein said second compound isselected from the group consisting of fluoxetine, fluvoxamine,sertraline, paroxetine, citalopram, escitalopram, sibutramine,duloxetine, and venlafaxine, and pharmaceutically acceptable salts orprodrugs thereof.
 8. The composition of claim 1, wherein said firstcompound is naltrexone and said second compound is fluoxetine.
 9. Thecomposition of claim 1, wherein said first compound is naltrexone andsaid second compound is bupropion.
 10. A method of affecting weightloss, comprising identifying an individual in need thereof and treatingthat individual to antagonize opioid receptor activity and to enhanceα-MSH activity.
 11. The method of claim 10, wherein said individual hasa body mass index greater than
 25. 12. The method of claim 10, whereinopioid receptor activity is antagonized by administering an opioidreceptor antagonist.
 13. The method of claim 12, wherein the opioidreceptor antagonist is a MOP receptor antagonist.
 14. The method ofclaim 10, wherein the opioid receptor antagonist is selected fromalvimopan, norbinaltorphimine, nalmefene, naloxone, naltrexone,methylnaltrexone, and nalorphine, and pharmaceutically acceptable saltsor prodrugs thereof.
 15. The method of claim 10, wherein α-MSH activityis enhanced by administering a compound that triggers the release ofα-MSH or increases the activity of neurons that express α-MSH.
 16. Themethod of claim 15, wherein said compound is a selective serotoninreuptake inhibitor (SSRI) or a specific 5-HT receptor agonist.
 17. Themethod of claim 16, wherein said SSRI is selected from fluoxetine,fluvoxamine, sertraline, paroxetine, citalopram, escitalopram,sibutramine, duloxetine, and venlafaxine, and pharmaceuticallyacceptable salts or prodrugs thereof.
 18. The method of claim 10,wherein said treating step comprises administering to said individual afirst compound and a second compound, wherein said first compound is anopioid antagonist and said second compound enhances α-MSH activity. 19.The method of claim 18, wherein said first compound and said secondcompound are administered nearly simultaneously.
 20. The method of claim10, wherein said treating step comprises administering to saidindividual a first compound and a second compound, wherein said firstcompound is an opioid antagonist and said second compound enhances α-MSHactivity.
 21. The method of claim 10, wherein said individual does notsuffer from depression, Prader-Willi syndrome, or binge eating disorder.